Stabilized dry rosin size



' diethylazobenzene,

Patented Sept. 1, 1942 v STABILIZED DRY ROSIN sizE Arthur 0. Dreshileld, Wilmington, Del., assignor to Hercules Powder Company,

Wilmington,

Del, a corporation of Delaware No Drawing. Application December 41, 1940,

Serial No. 368,453 7 4 Claims.

This invention relates to an improvement in rosin size and in particular concerns dry saponified rosin size compositions stabilized against atmospheric oxidation.

As is well known, rosin size may be prepared and utilized either in dry form. or as a liquid or paste in admixture with water. The dry form,

however, is in general deemed the most satisfactory because of its ease and economy of shipment, the type of dry'rosin size prepared by spray-drying saponified or partially saponified rosin being especially desirable because of its low density and high rate of solution in water.

The dry forms of rosin size, particularly the type formed by spray-drying, however, are disadvantageous in that they have a strong tendency to oxidize, and spontaneously decompose in the presence of air. Where, as is not uncommon, some free rosin is contained in the size, there is even a greater tendency to oxidize. Such oxidation, and consequent heating, is not only highly deleterious to the size itself but presents for about 48 hours when subjected to an accelerated oxidation treatment known as the Mackay a considerable fire hazard during storage and tion by oxidation or spontaneous combustion.

Thearomatic azo compounds which may be employed in preparing stabilized dry rosin size compositions according to the invention have the general formula wherein R represents a phenyl oranaphthyl group which may contain lower alkyl 'or lower alkoxy substituents. The terms lower alkyl and lower alkoxy refer'to alkyl and alkoxy groups containing less than five carbon atoms. Examples of such compounds are azobenzene, azonaphthalene, 2,2'-dimethylazobenzene,- 4,4-

2,2'-diisopropylazobenzene, 4,4-isopropoxyazobenzene, 2,2-diisobutylazobenzene, 3,3'-dimethoxyazobenzene, etc.

The proportion of anti-oxidant employed in preparing the stabilized d-ry size compositions of the invention depends upon a number of factors, among which are the particular anti-oxidant used and the degree of stabilization desired. Usually a size is considered sufficiently stabilized test. This treatment consists in. placing a sample of the stabilized size in a wire basket suspended in a water-jacketed chamber maintained at atemperature of 100 C. A small volume air is passed continuously through the chamber for the desired length of time, during which time the temperature of the sample, which is a measure of the oxidation, is accurately determined. Dry rosin size containing no anti-oxidant will oxidize to a considerable extent, i. e. its temperature will rise considerably above 100 C., and it may even ignite and burn when subjected to this test over a period of .about 48 hours, while a size stabilized according to the invention will undergo substantially no oxidation.

The optimum proportion of anti-oxidant also depends upon the composition of the size itself,

a somewhat larger proportion being required for sizes containing free alkali or free rosin. Thus, for example, a neutral saponiiied rosin size may be rendered stable to oxidation as determined by the 48-hour Mackay test by the addition of 1.0

per cent by weight of azobenzene, whereas a size containing 0.3-0.6 per cent by weight of free alkali may require the addition of 2.0 per cent by weight of azobenzene to securesuch a degree of stabilization. Similarly, sizes containing 5.010.0 per cent by weight of free rosin may require the use of 1.5-2.0 per cent by weight of the anti-oxidant to secure good stabilization. The type of dry size, i. e. whether it has been prepared from wood rosin, gum rosin,. or rosin which hasbeen heat-treated to effect partial dccarboxylation, is also of influence on the proportion of anti-oxidant to be used. Thus, sizes comprising. saponified gum rosin usually require a somewhat larger proportion of the anti-oxidant than the other types. In general, however, it will be found that from about 1.0-2.5 per cent of the anti-oxidant, based on the weight of the rosin used in preparing the size, will be sufilcient to render any size substantially resistant to oxidation.

The anti-oxidant may be incorporated with the size at any convenient time during the process for the production ofthe size, by treatment of the size after it is produced, or by treatment of the rosin prior to its saponification. Ordinarily, however, the anti-oxidant will desirably for all ordinary purposes if it resists oxidation addition consists in dissolving the anti-oxidant in a-suitable solvent andadding the resultant" solution to the mixture of water, alkali, and rosin in the reaction vessel in which the saponiflcaq tion reaction is carried out. Thus, for example, about 1.5 per cent of azobenzene, based on the weight of the rosin employed, may be dissolved in alcohol and added toa mixture of rosin, water,

and sodium hydroxide so proportioned as to produce a size containing about 5.0 per cent free rosin, either before or during the saponification reaction. Upon completion of the reaction, the mixture may be desiccated by spray or' drum drying to produce a dry size having theantioxidant uniformly distributed therethrough.

The following example illustrates one way in sure of about 125 lbs./sq. in. while venting the autoclave to maintain a pressure of about 85 lbs./sq. in. The mixture is then heated at a temperature of about 176 C. for 10 minutes after which is added 0.4 pound of azobenzene in 3 per cent paraffin oil solution. The heating. is continued for 10 minutes after which the mixture is allowed to discharge into a drying chamber whereby it is desiccated to form a dry powder having the anti-oxidant uniformly dispersed therethrough.

A sample of a dry rosin size stabilized with azobenzene as described above was stable to oxidation in the air as determined by the 48-hour Mackay test, whereas a size containing no azobenzene ignited and bumed'in 13 hours. Similarly, the stabilized'size had an oxygen demand of 0.93 per cent as determined by the standard oxygen demand test in an oxygen absorption train over a two-hour period, whereas an'unstabilized size had an oxygen demand of about 2.4 per cent.

' invention may be employed instead of those explained, change being made as regards the materials employed, provided the ingredients stated by any of the appended claims or the equivalent of such stated ingredients be employed.

This application is a continuation-in-part ofv my copending application Serial No. 152,194, filed July 6 1937.

What I claim and desire to protect by Letters Patent is: g

1. A stabilized dry size composition comprising saponified rosin and, as an anti-oxidant therefor, an aromatic azo compound having the general formula wherein R represents an aromatic radical .selected from the group consistingof phenyl, naphthyl and lower alkyl and lower alkoxy substituted phenyl and naphthyl radicals, said azo compound being present in an amount suflicient to render the composition substantially resistant to oxidation. 7

2. A stabilized dry size composition comprising saponified rosin, free rosin, and. as an anti-oxidant therefor, an aromatic azo compound having the general formula wherein R represents an aromatic radical selected from the group consisting of phenyl, naphthyl and lower alkyl and lower alkoxy substituted phenyl and naphthyl radicals, said azo. compound being present in an amount sufficient to render the composition substantially resistant to oxidation.

3. A stabilized dry size composition comprising saponified rosin and,as an anti-oxidant therefor, azobenzene in an amount sufllcient to render the composition substantially, resistant to oxida-' tion.

4. A stabilized dry size composition comprising saponified rosin, free rosin, and, as an anti-oxidant therefor, azobenzene in an amount suflicient to render the composition substantially resistant to oxidation.

ARTHUR C. DRESHFIELD. 

